Removal of ketene impurities in the preparation of alpha-cyano-aryloxybenzyl alcohols

Abstract

An improved process for preparation of insecticidal esters of alpha-cyano-m-aryloxybenzyl alcohols is disclosed which includes the steps of preparing an acid chloride of the formula: ##STR1## by reacting the corresponding acid with thionyl chloride, purifying the acid chloride thus obtained by fractional distillation and reacting the purified acid chloride with a phenoxybenzaldehyde and a cyanide solution to yield the desired insecticidal product. In this improved process, the presence of difficult to remove ketene reaction products in the final insecticidal product is avoided by treating the purified acid chloride with an ahydrous hydrogen halide prior to reaction with the phenoxybenzaldehyde.

What is claimed is: 
     
       1. In the process for the preparation of insecticidal esters of alpha-cyano-m-aryloxybenzyl alcohols by the steps of preparing an acid chloride of the formula: ##STR7## a secondary alkyl group of from 3 to 6 carbon atoms and Y represents a hydrogen atom or halogen atom of atomic number 9 to 35, inclusive, by reacting the corresponding acid with thionyl chloride, purifying the acid chloride thus obtained by fractional distillation and reacting the purified acid chloride with a phenoxybenzaldehyde and a cyanide solution to yield the desired insecticidal product, the improvement which comprises reacting the purified acid chloride with anhydrous hydrogen chloride under conditions which substantially convert a ketone impurity of the formula: ##STR8## which is generated and/or carried over in said distillation and is present in the purified acid chloride to the desired acid chloride, thereby avoiding further reaction of the ketene with said cyanide solution to yield an impurity which contaminates the desired insecticidal product. 
     
     
       2. The improvement according to claim 1, in which Y is a chlorine atom. 
     
     
       3. The improvement according to claim 2, in which R is an isopropyl group. 
     
     
       4. The improvement according to claim 3, in which said phenoxybenzaldehyde is m-phenoxybenzaldehyde. 
     
     
       5. The improvement according to claim 4, in which said cyanide solution is an aqueous sodium cyanide solution.